This invention relates to methods of preparing sodium-hydrogen exchanger type 1 (NHE-1) inhibitors and methods of preparing pharmaceutical compositions comprising the NHE-1 inhibitors.
Sodium-hydrogen exchanger type 1 (NHE-1) inhibitors of formula Ixe2x80x2
are useful for the prevention and treatment of myocardial ischemic injury. Myocardial ischemic injury can occur in out-patient as well as in perioperative settings and can lead to the development of sudden death, myocardial infarction or congestive heart failure. It is anticipated that therapies using the NHE-1 inhibitors of formula Ixe2x80x2 will be life-saving and reduce hospitalizations, enhance quality of life and reduce overall health care costs of high risk patients.
Commonly assigned WO 99/43663A1, discloses a variety of NHE-1 inhibitors including NHE-1 inhibitors relating to the methods of the present invention.
Baumgarth, et al. (1997) J. Med. Chem. 40, 2017-2034 discloses synthesizing acyl guanidine via coupling of an ester and guanidine, in addition to an acid chloride and guanidine wherein the substrates are aromatic monocyclic structures.
Ferlin, et al. (1989) II Famraco 44:12, 1141-1156 disclose a method of synthesizing 5-hydrazinoquinoline by reacting quinolin-5-ylamine with stannous chloride and sodium nitrite.
Colored impurities are produced when N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine, an NHE-1 inhibitor of formula Ixe2x80x2, is prepared by the previously known processes. For example, aqueous solutions of N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine made by the previously known processes have a distinct yellow color. The impurities responsible for such coloration have not been identified.
From a commercial and regulatory point of view, discoloration of pharmaceutical products containing N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine is undesirable. In the case of pharmaceutical products that are administered to patients, especially those administered by injection, it is considered commercially advantageous that such products be substantially colorless and in as pure a form as possible. For example, a colorless product is helpful for conducting blinded clinical research using a placebo, ensuring that the placebo is visually indistinguishable from the active product.
This invention provides improved processes for preparing NHE-1 inhibitors of formula 
wherein R1 is methylsulfonyl or hydrogen, R2 is hydrogen or a halogen, R3 is hydrogen, R4 is hydrogen or a halogen, or R3 and R4, together with the carbon atoms to which they are attached, form a six member fully unsaturated ring having one hetero atom that is nitrogen.
In one aspect, this invention provides methods of preparing a compound of formula Ixe2x80x2
comprising: combining a mixture of acetonitrile and a compound of formula IXxe2x80x2
with thionyl chloride to form a mixture comprising a compound of formula Xxe2x80x2; 
evaporating excess thionyl chloride from said mixture to form an evaporated mixture; and combining said evaporated mixture with guanidine to form a compound of formula Ixe2x80x2, wherein R1 is methylsulfonyl or hydrogen, R2 is hydrogen or a halogen, R3 is hydrogen, R4 is hydrogen or a halogen, or R3 and R4 form, together with the carbon atoms to which they are attached, a six member fully unsaturated ring having one hetero atom that is nitrogen.
In another aspect, the invention provides methods of preparing a pharmaceutical composition comprising: combining a mixture of acetonitrile and a compound of formula IXxe2x80x2
with thionyl chloride to form a mixture comprising a compound of formula Xxe2x80x2; 
evaporating of excess thionyl chloride from said mixture to form an evaporated mixture; combining said evaporated mixture with guanidine to form a final mixture comprising a compound of formula Ixe2x80x2
isolating said compound of formula Ixe2x80x2 from said final mixture; and combining said compound of formula Ixe2x80x2, or a pharmaceutically acceptable salt thereof, with a pharmaceutically acceptable vehicle, diluent or carrier, wherein R1 is methylsulfonyl or hydrogen, R2 is hydrogen or a halogen, R3 is hydrogen, R4 is hydrogen or a halogen, or R3 and R4 form, together with the carbon atoms to which they are attached, a six member fully unsaturated ring having one hetero atom that is nitrogen.
In a preferred embodiment of the invention, the compound of formula IXxe2x80x2 is 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid, the compound of formula Xxe2x80x2 is 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl chloride and the compound of formula Ixe2x80x2 is N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine.
In a more preferred embodiment, the 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid in acetonitrile is combined with thionyl chloride at a temperature of about 25xc2x0 C. for at least about one hour and preferably for at least about one-half hour.
In another preferred embodiment, the evaporation of thionyl chloride reduces the volume of the mixture by about 10%. More preferably, said evaporation is performed under vacuum and at a temperature of about 85xc2x0 C.
Unless otherwise defined below, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs.
xe2x80x9cHalogenxe2x80x9d means an atom of one of the elements of Group 18 of the periodic table of elements, preferably fluorine, bromine or chlorine.
xe2x80x9cPharmaceutically-acceptable saltxe2x80x9d refers to nontoxic anionic salts containing anions such as (but not limited to) chloride, bromide, iodide, sulfate, bisulfate, phosphate, acetate, maleate, fumarate, oxalate, lactate, tartrate, citrate, gluconate, methanesulfonate and 4-toluene-sulfonate. Where more than one basic moiety exists, multiple salts (e.g., di-salt) are included. The expression also refers to nontoxic cationic salts such as (but not limited to) sodium, potassium, calcium, magnesium, ammonium or protonated benzathine (N,Nxe2x80x2-dibenzylethylenediamine), choline, ethanolamine, diethanolamine, ethylenediamine, meglamine (N-methyl-glucamine), benethamine (N-benzylphenethylamine), piperazine or tromethamine (2-amino-2-hydroxymethyl-1,3-propanediol).
Those skilled in the art will recognize, based on the present description, that certain compounds of this invention will contain one or more atoms that may be in a particular stereochemical or geometric configuration, giving rise to stereoisomers and configurational isomers. All such isomers and mixtures thereof are included in this invention.
Reaction Scheme A illustrates processes of preparing compounds of formula VIxe2x80x2. Scheme B illustrates processes of preparing compounds of formula Ixe2x80x2 using compounds of formula VIxe2x80x2 from Scheme A. These processes are used to make NHE-1 inhibitors, including, for example, N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine. 
According to Scheme A, a diazonium salt of a compound of formula IIxe2x80x2 is combined with L-ascorbic acid (formula III) to form a lactone intermediate compound of formula IVxe2x80x2 as a transient intermediate, which decomposes to an oxalic acid intermediate compound of formula Vxe2x80x2. At elevated reaction temperatures, above about 35xc2x0 C. and preferably above about 50xc2x0 C. and most preferably above about 80xc2x0 C., a compound of formula IVxe2x80x2 converts to a formula VIxe2x80x2 compound as a one-pot reaction. At lower temperatures, the oxalic acid intermediate compounds of formula Vxe2x80x2 are not converted to compounds of formula VIxe2x80x2. An oxalic compound of formula Vxe2x80x2 may be converted to a hydrazino compound of formula VIxe2x80x2 using a hydrolyzing agent, preferably hydrochloric acid. Using concentrated hydrochloric acid will result in formation of a compound of formula VIxe2x80x2 as the hydrochloride salt.
As noted above, the lactone intermediates of formula IVxe2x80x2 are unstable and decompose under the reaction conditions into the corresponding oxalic acid derivative. However, when the diazonium salt of formula IIxe2x80x2 is derived from 2,5-dichlorophenylaniline, the lactone intermediate may be isolated.
Scheme B illustrates the process of preparing a compound of formula Ixe2x80x2. A hydrazino compound of formula VIxe2x80x2 is combined with the compound of formula VII in an inert solvent such as, for example, ethyl acetate at a temperature of about 20xc2x0 C. for about one hour followed by heating to a temperature of about 75xc2x0 C. for about five hours to form a pyrazole compound of formula VIIIxe2x80x2.
The compound of formula VII may be prepared by combining methyl-3-cyclopropyl-3-oxopropanoate in ethyl acetate with N,N-dimethylformamide dimethylacetal at a temperature of about 65xc2x0 C. to about 75xc2x0 C. for about 4 hours.
A pyrazole compound of formula VIIIxe2x80x2 is then hydrolyzed with a base, such as, for example, sodium hydroxide, lithium hydroxide or potassium hydroxide, in a solvent such as water and/or methanol and/or THF at ambient temperature or at an elevated temperature (e.g., reflux) for about one hour to about five hours to prepare an acid of formula IXxe2x80x2.
An acid of formula IXxe2x80x2 is activated with a coupling agent such as thionyl chloride at an elevated temperature of about 60xc2x0 C. to about 90xc2x0 C. for about 13 hours to form the acid chloride compound of formula Xxe2x80x2. Those skilled in the art will appreciate, based upon the present description, that other suitable coupling agents may be used. A suitable coupling agent is one which transforms the carboxylic acid into a reactive species which forms an acyl guanidine on reaction with guanidine. The coupling agent can convert the carboxylic acid to an activated intermediate which is isolated and/or formed in a first step and allowed to react with guanidine in a second step. Examples of such coupling agents and activated intermediates include thionyl chloride or oxalyl chloride to form the acid chloride, cyanuric flouride to form an acid flouride or an alkyl chloroformate such as isobutyl or isopropenyl chloroformate or propanephosphonic anhydride to form a mixed anhydride of the carboxylic acid, or carbonyldimidazole to form an acylimidazole. Alternatively, the coupling agent may be a reagent which effects coupling in a one pot process. Exemplary coupling reagents are 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride-hydroxybenzotriazole (EDC/HOBT), dicyclohexylcarbodiimide/hydroxybenzotriazole (DCC/HOBT),2-ethoxy-1-ethoxycarbonyl-,2dihydroquinoline (EEDQ) and diethylphosphoryl-cyanide. The coupling is performed in an inert solvent, preferably an aprotic solvent, in the presence of excess guanidine. Exemplary solvents include acetonitrile, dichloromethane, dimethylformamide and chloroform or mixtures thereof. Use of these coupling agents and appropriate selection of solvents and temperatures are known to those skilled in the art, based upon the present description, or can be readily determined from the literature in light of this disclosure. These and other exemplary conditions useful for coupling carboxylic acids are described, for example, in Houben-Weyl, Vol XV, part II, E. Wunsch, Ed., G. Theime Verlag, 1974, Stuttgart; M. Bodansky, Principles of Peptide Synthesis, Springer-Verlag, Berlin 1984; and The Peptides, Analysis, Synthesis and Biology (ed. E. Gross and J. Meienhofer), vols 1-5 (Academic Press, NY 1979-1983).
A compound of formula Xxe2x80x2 is coupled with guanidine to form the NHE-1 inhibitor of formula Ixe2x80x2 by combining a formula Xxe2x80x2 compound with guanidine hydrochloride and an inorganic base, such as sodium hydroxide, lithium hydroxide or potassium hydroxide, in a solvent which is preferably selected from water, methanol and tetrahydrofuran.
In a preferred embodiment of the reactions of Scheme A and Scheme B, the formula IIxe2x80x2 compound is a diazonium salt of 5-aminoquinoline. The diazonium salt of 5-aminoquinoline is combined with ascorbic acid to form the compound of formula VIxe2x80x2 that is 5-hydrazinoquinoline. The pyrazole compound of formula VIIIxe2x80x2 that is formed is 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid methyl ester.
Prior to the coupling step with guanidine, 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid methyl ester is preferably treated with citric acid to remove red impurities. In this treatment, the solvent solution containing 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid methyl ester is combined with an aqueous solution of citric acid to form a darker red aqueous layer and a red organic layer. The aqueous layer is discarded, leaving the organic layer containing citric acid purified 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid methyl ester.
5-Cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid methyl ester is hydrolyzed with a base such as sodium hydroxide in water to form 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid, analogous to an acid of formula IXxe2x80x2.
5-Cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid is then activated with a coupling agent such as thionyl chloride to form the chloride compound, analogous to the formula Xxe2x80x2 compound. For the activation reaction, 5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carboxylic acid is combined with dry acetonitrile to form a slurry. Thionyl chloride is added to the slurry and the mixture is heated to about 25xc2x0 C. preferably for at least about one-half hour, more preferably for at least about one hour. Unreacted thionyl chloride and dissolved HCl gas is then removed by atmospheric distillation. Preferably, the volume of the mixture is reduced by about 10%. The resulting slurry containing the chloride activated compound of formula Xxe2x80x2 is then coupled with guanidine to form the NHE-1 inhibitor, N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine. For coupling reaction the slurry is added to an aqueous guanidine solution at pH 14.
Those skilled in the art will appreciate, based upon the present disclosure, that the use of acetonitrile in the chloride activation reaction is particularly advantageous for a commercial production process in that the required reaction time with thionyl chloride is relatively short, i.e. approximately one-half to one hour. Likewise, the removal of thionyl chloride by distillation following formation of the chloride compound is advantageous in that it eliminates the cumbersome additional step of isolating the activated chloride compound prior to the guanidine coupling reaction to form the NHE-1 inhibitor. Moreover, it will be appreciated that the distillation step also eliminates the need to use a second solvent for resuspension of the recovered chloride for use in the guanidine coupling reaction.
N-(5-Cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine prepared by a method of this invention may be converted to a pharmaceutically acceptable salt. For example N-(5-cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine may be converted to its mesylate salt, for example, by combining the compound with methanesulfonic acid, preferably in a suitable polar aprotic solvent at a temperature of about 40xc2x0 C. to about 80xc2x0 C. Suitable polar aprotic solvents preferably include a mixture of acetone and 1-methyl-2-pyrrolidonone. Conversion to other pharmaceutically acceptable salts may be performed using processes known in the art, based upon the present description.
N-(5-Cyclopropyl-1-quinolin-5-yl-1H-pyrazole-4-carbonyl)-guanidine monomesylate, when prepared by the chemical processes and methods described above, gives rise to a 1% aqueous solution having very low blue light absorption. For example, at 450 nm the light absorption of a 1% solution is in the range 0.007-0.005. As noted above, previous procedures give rise to distinctly yellow solutions with absorption levels in the range 0.027-0.025. Light absorption is calculated according to the formula, A=log10(I0/I), wherein xe2x80x9cI0xe2x80x9d is incident light and xe2x80x9cIxe2x80x9d is transmitted light.
In another preferred embodiment, the formula IIxe2x80x2 compound is a diazonium salt of 2-chloro-4-methanesulfonyl-phenylamine. The diazonium salt is combined with ascorbic acid to form a compound of formula VIxe2x80x2 that is 2-chloro-4-methanesulfonyl-2-phenylhydrazine. The formula VIIIxe2x80x2 pyrazole formed is 5-cyclopropyl-1-(2-chloro-4-methanesulfonylphenyl)-1H-pyrazole-4-carboxylic acid methyl ester.
5-Cyclopropyl-1-(2-chloro-4-methanesulfonylphenyl)-1H-pyrazole-4-carboxylic acid methyl ester is hydrolyzed with a base such as sodium hydroxide in water to form 5-cyclopropyl-1-(2-chloro-4-methanesulfonylphenyl)-1H-pyrazole-4-carboxylic acid, analogous to an acid of formula IXxe2x80x2. The carboxylic acid pyrazole is then activated with coupling agent such as thionyl chloride to form the activated compound, analogous to a compound of formula Xxe2x80x2. The activated compound is then coupled with guanidine to form the NHE-1 inhibitor, N-{5-cyclopropyl-1-(2-chloro-4-methanesulfonylphenyl)-1H-pyrazole-4-carbonyl}-guanidine.
The starting material and reagents for the above described compounds are commercially available or can be easily synthesized by those skilled in the art using conventional methods of organic synthesis.
Administration of the compounds prepared by a method of this invention can be via any method which delivers a compound of this invention preferentially to the desired tissue (e.g., liver and/or cardiac tissues). These methods include, for example, oral routes, parenteral and intraduodenal routes. Generally, the compounds of the present invention may be administered in single (e.g., once daily) or multiple doses or via constant infusion.
The compounds prepared by a method of this invention are useful, for example, in reducing or minimizing damage effected directly to any tissue that may be susceptible to ischemia/reperfusion injury (e.g., heart, brain, lung, kidney, liver, gut, skeletal muscle, retina) as the result of an ischemic event (e.g., myocardial infarction). The compounds can be used to prevent (i.e. prospectively or prophylactically), blunt or stem, tissue damage (e.g., myocardial tissue) in patients who are at risk for ischemia (e.g., myocardial ischemia).
The compounds prepared by a method of this invention can be administered in any suitable manner, including, for example, orally, or parenterally (e.g., intravenous, intramuscular, subcutaneous or intramedullary). Topical administration may also be indicated, for example, where the patient is suffering from gastrointestinal disorders or whenever the medication is best applied to the surface of a tissue or organ as determined by the attending physician, based upon the present description.
The amount of administration as well as the timing of administration will be dependent on the subject being treated, on the severity of the affliction, on the intended manner of administration and on the judgement of the prescribing physician, based upon the present description. Thus, because of patient to patient variability, the dosages given below are a guideline and the physician may titrate doses of the drug to achieve the treatment that the physician considers appropriate for the patient. In considering the degree of treatment desired, the physician must balance a variety of factors such as age of the patient, presence of preexisting disease, as well as presence of other diseases (e.g., cardiovascular disease).
For example, in one mode of administration, the compounds prepared by a method of this invention may be administered just prior to surgery (e.g., within twenty-four hours before surgery for example cardiac surgery) during or subsequent to surgery (e.g., within twenty-four hours after surgery) where there is risk of myocardial ischemia. The compounds may also be administered in a chronic daily mode.
Amounts of the compounds prepared by a method of this invention are used that are effective for ischemic protection. A preferred dosage is about 0.001 to 100 mg/kg/day of the compounds. An especially preferred dosage is about 0.01 to 50 mg/kg/day of the compounds.
The compounds of the present invention can be administered in the form of a pharmaceutical composition comprising at least one of the compounds of this invention together with a pharmaceutically acceptable vehicle, carrier or diluent. Thus, the compounds of this invention can be administered individually or together in any conventional oral, parenteral, rectal or transdermal dosage form.
For oral administration a pharmaceutical composition can take the form of solutions, suspensions, tablets, pills, capsules, powders, and the like. Tablets containing various excipients such as sodium citrate, calcium carbonate and calcium phosphate are employed along with various disintegrants such as starch and preferably potato or tapioca starch and certain complex silicates, together with binding agents such as polyvinylpyrrolidone, sucrose, gelatin and acacia. Additionally, lubricating agents such as magnesium stearate, sodium lauryl sulfate and talc are often very useful for tabletting purposes. Solid compositions of a similar type are also employed as fillers in soft and hard-filled gelatin capsules; preferred materials in this connection also include lactose or milk sugar as well as high molecular weight polyethylene glycols. When aqueous suspensions and/or elixirs are desired for oral administration, the compounds of this invention can be combined with various sweetening agents, flavoring agents, coloring agents, emulsifying agents and/or suspending agents, as well as such diluents as water, ethanol, propylene glycol, glycerin and various like combinations thereof.
For purposes of parenteral administration, solutions, for example, in sesame or peanut oil or in aqueous propylene glycol can be employed, as well as sterile aqueous solutions of the corresponding water-soluble salts. Such aqueous solutions may be suitably buffered, if necessary, and the liquid diluent first rendered isotonic with sufficient saline or glucose. These aqueous solutions are especially suitable for intravenous, intramuscular, subcutaneous and intraperitoneal injection purposes. In this connection, the sterile aqueous media employed are all readily obtainable by standard techniques well-known to those skilled in the art.
For purposes of transdermal (e.g.,topical) administration, dilute sterile, aqueous or partially aqueous solutions (usually in about 0.1% to 5% concentration), otherwise similar to the above parenteral solutions, are prepared.
Methods of preparing various pharmaceutical compositions with a certain amount of active ingredient are known, or will be apparent in light of this disclosure, to those skilled in this art. For examples of methods of preparing pharmaceutical compositions, see Remington: The Science and Practice of Pharmacy, Mack Publishing Company, Easton, Pa., 19th Edition 1995.
Pharmaceutical compositions according to the invention may contain for example 0.0001%-95% of the compounds prepared by a method of this invention. In any event, the composition or formulation to be administered will contain a quantity of the compound(s) prepared according to the invention in an amount effective to treat the disease, condition or disorder of the subject being treated.
The disclosures of all patents, applications, publications and documents, for example brochures or technical bulletins, cited herein, are hereby expressly incorporated by reference in their entirety.